There are two types of electrical currents: alternating current (or AC for “alternative current”) and direct current (or DC for “direct current”). How do they work? What differences do they present in terms of charging electric vehicles ? Which should you prefer?
The difference between DC current and AC current
DC current and AC current are two types of electrical currents that are an integral part of our daily lives, for different but complementary uses.
DC current: operation
Direct current is constantly flowing in one direction only. DC current is produced by the chemical activity of generators (batteries, batteries , accumulators, solar panels...). This is what we use for example for our phones or our flashlights.
It is a storable type of current: you can use it without being connected to the electrical network.
DC was the first to be used. Thomas Edison, a pioneer in electricity, put it in place when creating the first electrical network in New York. But, poorly suited to this use, power outages were frequent.
The AC current: operation
Alternating current is currently the most used: it is the one delivered to you by your electricity supplier. Unlike direct current, it flows in one direction and then in another. It carries equal electrical charges at regular intervals. In France, electrons change direction 50 times per second. La
The frequency used is therefore 50 hertz.
The AC current is produced in a power plant, using an alternator. It is sent via power lines to electrical transformers. Intensity sound
then drop so that it can be distributed to our homes.
AC current is used for our network because it is easier to transport and transform, while limiting losses. It is Nikola Tesla who is the pioneer.
Charging an electric vehicle: DC current or AC current?
The current in the electrical network is therefore always alternating. In this case, what do we do to have direct current in our phones and other devices? Simply through the use of a converter (or charger).
For everyday portable electronic devices (telephones, computers, lamps, etc.), the converter is generally placed inside the electrical outlet.
When it comes to charging electric vehicles, AC must also be converted to DC. The converter is located here inside the car.
When it comes to electric car charging stations, it is possible to recharge using DC or AC. How does it work and what current should be preferred for an electric car?
DC current for electric cars: “super charger”
When you charge your electric vehicle in DC, the charger with which the electric vehicle is equipped and which converts alternating current into direct current, becomes superfluous. The terminal itself converts the current to inject it directly into the battery.
The main advantage of DC terminals lies in their charging speed: you can charge your car 10, 20, or even up to 50 times faster than with a regular household outlet.
They can be found for example on highway areas: they allow you to recharge your electric car quickly, while you can stretch your legs or have a coffee.
As these terminals contain a converter, they are more bulky, but also more expensive: in general more than €50,000.
Although it is the best method for quickly recharging an electric car, this type of charging station also has other disadvantages. In fact, it requires a great deal of current from the electrical network (around 125 A). Its costs (production, installation and operation) are also very high. The result? Higher charging rates.
In addition, charging your car too regularly with a DC terminal damages the vehicle's batteries.
These terminals are therefore not very suitable for use at home or in business.
AC current for electric cars: more economical and more suitable for daily use
Charging electric vehicles with AC current is the most frequent. When you plug an electric vehicle into an AC charging station, the current is converted inside the vehicle before it enters the battery.
The charging speed then depends on two factors:
- The output power of the terminal
- The power of the vehicle charger to convert the current to DC
This is the most suitable method when you park your car for more than 20 minutes: when you are working or going home for example. In just a few hours, your EV battery will be full again.
AC terminals are less expensive than DC terminals, in terms of their production, installation and operation. This therefore makes it possible to have a much more interesting charging cost than with a DC terminal.
Finally, their regular use does not affect the vehicle's batteries. In the long run, it is therefore a better solution.
To summarize, if you need to recharge your EV quickly, while doing some shopping, the DC terminal will be the most suitable, at a higher charging cost. On the other hand, on a daily basis, it is more interesting to charge your electric car with an AC terminal, from a financial point of view, but also for the durability of your vehicle's batteries.
Qovoltis offers smart charging stations, with two charging modes: optimized or fast, adapted to your needs. Thanks to an application on your smartphone, you have total control of your refills in real time. This also allows transparent pricing with respect to the kWh consumed.
Sources: Total, Knowledge of energies, Butagaz, Engie, EDF.
